This application relates to a cooling scheme for a gas turbine engine component, such as a stationary vane, wherein an impingement tube is located within a cooling air channel, and pedestals are aligned with a portion of the tube.
Gas turbine engines are provided with a number of functional sections, including a fan section, a compressor section, a combustion section, and a turbine section. Air and fuel are combusted in the combustion section. The products of the combustion move downstream, and pass over a series of turbine rotors, driving the rotors to create power.
Numerous components within the gas turbine engine are subject to high levels of heat during operation. As an example, a turbine section will have a plurality of vanes over which high temperature products of combustion pass. Cooling fluid, and typically air, is passed within a body of the vanes to cool the vanes.
A number of approaches have been made to cool the stationary vanes. One type of cooling is film cooling. In film cooling, air is directed from an internal cavity in the vane to an outer surface. This air creates a film passing along the outer surface, and is much cooler than the products of combustion. The film cooling thus cools an outer surface of the vane. For various reasons, the location and amount of film cooling may be limited.
Other cooling schemes include the use of impingement air being directed through an impingement tube and off of an inner wall of the vane. The purpose of this impingement cooling air flow is to cool the inner wall.
In one particular cooling scheme arrangement known for vanes, an impingement tube directs air through impingement holes and against inner walls of the vane at both a suction side and a pressure side. The impingement tube is positioned in a mid-location between a cavity rib and a pedestal array. Air having passed through impingement holes at both the pressure side and the suction side, then passes downstream between the impingement tube and an inner wall, and then over the trailing edge pedestal array the air exits through exit holes at the trailing edge. Further, a film cooling hole is provided on the suction side forwardly of a gage point. This position is utilized to reduce certain aerodynamic losses. The air having left this film cooling hole passes along the suction side to cool the wall. However, the cooling provided by this film cooling air degrades along a direction toward the trailing edge. Thus, and in an area roughly adjacent with an end of the impingement tube area, there is a portion of the suction wall that may not receive adequate cooling.
In addition to this degradation, the impingement in this region also becomes somewhat ineffective due to “cross-flow degradation.” This is the result of the accumulation of coolant that has been injected from earlier regions. As more flow enters the cavity between the tube and the wall and heads toward the trailing edge, the impingement jets begin to become less effective.
The present invention is directed to addressing this concern.